Feldspar Samples Research Articles

The immersion mode ice nucleation behavior of mineral dusts: A comparison of different pure and surface modified dusts

AbstractIn this study we present results from immersion freezing experiments with size‐segregated mineral dust particles. Besides two already existing data sets for Arizona Test Dust (ATD), and Fluka kaolinite, we show two new data sets for illite‐NX, which consists mainly of illite, a clay mineral, and feldspar, a common crustal material. The experiments were carried out with the Leipzig Aerosol Cloud Interaction Simulator. After comparing the different dust samples, it became obvious that the freezing ability was positively correlated with the K‐feldspar content. Furthermore, a comparison of the composition of the ATD, illite‐NX, and feldspar samples suggests that within the K‐feldspars, microcline is more ice nucleation active than orthoclase. A coating with sulfuric acid leads to a decrease in the ice nucleation ability of all mineral dusts, with the effect being more pronounced for the feldspar sample.

Assessing Optically Stimulated Luminescence (OSL) signal contamination within small aliquots and single grain measurements utilizing the composition test

Quartz in tectonically active regions can suffer from signal contamination when utilized for Optically Stimulated Luminescence (OSL) dating. Typically, these environments bring quartz-bearing bedrock to the surface, which erodes and enters geomorphic systems with little fluvial reworking, resulting in dim OSL signal response. Conversely, feldspars often have an inherently brighter signal, even among bedrock or freshly eroded samples. Environments with dim quartz can be difficult to date as the signal contribution from errant feldspars may dominate the measured signal. Further, immature sediments may retain mineral inclusions within quartz grains that would have been physically or chemically eroded in more mature sediments. Previously, we presented a signal composition test which utilizes thermal quenching and IR bleaching susceptibility to assess the purity of a quartz sample. Additional measurements have been made, looking at the systematics of how small volumes of feldspar can affect the results of aliquots analyzed with this composition test. Further, different feldspar samples have been assessed for their response to the composition test and chemical compositions were determined using energy-dispersive X-ray (EDX) spectroscopy with a scanning electron microscope (SEM). Finally, we present a single grain protocol for the composition test.

Mathematical characterization of continuous wave infrared stimulated luminescence signals (CW-IRSL) from feldspars

Continuous-wave infrared stimulated luminescence signals (CW-IRSL) from feldspars have been the subject of many experimental studies, due to their importance in luminescence dating and dosimetry. Accurate mathematical characterization of the shape of these CW-IRSL signals in feldspars is of practical and theoretical importance, especially in connection with “anomalous fading” of luminescence signals in dating studies. These signals are known to decay in a non-exponential manner and their exact mathematical shape as a function of stimulation time is an open research question. At long stimulation times the IRSL decay has been shown experimentally to follow a power law of decay, and previous researchers have attempted to fit the overall shape of these signals empirically using the well known Becquerel function (or compressed hyperbola decay law). This paper investigates the possibility of fitting CW-IRSL curves using either the Becquerel decay law, or a recently developed analytical equation based on localized electronic recombination of donor–acceptor pairs in luminescent materials. It is shown that both mathematical approaches can give excellent fits to experimental CW-IRSL curves, and the precision of the fitting process is studied by analyzing a series of curves measured using a single aliquot of a feldspar sample. Both fitting equations are solutions of differential equations involving numerically similar time dependent recombination probabilities k(t). It is concluded that both fitting equations provide approximately equivalent mathematical descriptions of the CW-IRSL curves in feldspars, and can be used as mathematical representations of the shape of CW-IRSL signals.

Space weathering of silicate regoliths with various FeO contents: New insights from laser irradiation experiments and theoretical spectral simulations

To investigate effects of micrometeorite bombardment on optical spectra and composition of planetary and asteroid regoliths with low Fe contents, we irradiated samples of a Fe-poor plagioclase feldspar (andesine–labradorite) using a nanosecond pulsed laser. We measured reflectance spectra of irradiated and non-irradiated areas of the samples (pressed pellets) between 0.5 and 18μm and performed SEM/EDS and TEM studies of the samples. Bulk FeO content of 0.72wt.% in the samples is comparable, for example, to FeO content in silicates on the surface of Mercury, that was recently mapped by NASA’s MESSENGER mission and will be spectrally mapped by remote sensing instruments MERTIS and SYMBIO-SYS on board the ESA BepiColombo spacecraft. We also employed theoretical spectral modeling to characterize optical alteration caused by formation of nano- and submicrometer Fe0 inclusions within space-weathered surface layers and grain rims of a Fe-poor regolith. The laser-irradiated surface layer of plagioclase reveals significant melting, while reflectance spectra show mild darkening and reddening in the visible and near-infrared (VNIR). Our spectral modeling indicates that the optical changes observed in the visible require reduction of bulk FeO (including Fe from mineral impurities found in the sample) and formation of nanophase (np) Fe0 within the glassy surface layer. A vapor deposit, if present, is optically too thin to contribute to optical modification of the investigated samples or to cause space weathering-induced optical alteration of Fe-poor regoliths in general. Due to low thickness of vapor deposits, npFe0 formation in the latter can cause darkening and reddening only for a regolith with rather high bulk Fe content. Our calculations show that only a fraction of bulk Fe is likely to be converted to npFe0 in nanosecond laser irradiation experiments and probably in natural regolith layers modified by space weathering. The previously reported differences in response of different minerals to laser irradiation, and probably to space weathering-induced heating are likely controlled by their differences in electrical conductivities and melting points. For a given mineral grain, its susceptibility to melting/vaporization is also affected by electric conductivities of adjacent grains of other minerals in the regolith. Published nanosecond laser irradiation experiments simulate optical alteration of immature regoliths, since only the uppermost surface layer of an irradiated pellet is subject to heating. According to our calculations, if regolith particles due to impact-induced turnover are mantled with npFe0-bearing rims of the same thickness, then even low contents of Fe similar to our sample or Mercury’ surface can cause significant darkening and reddening, provided a melt layer, rather than a thin vapor deposit is involved into npFe0 formation. All spectral effects observed in the thermal infrared (TIR) after irradiation of our feldspar sample are likely to be associated with textural changes. We expect that mineralogical interpretation of the BepiColombo MERTIS infrared spectra of Mercury between 7 and 17μm will be influenced mostly by textural effects (porosity, comminution) and impact glass formation rather than formation of npFe0 inclusions.

On the shape of continuous wave infrared stimulated luminescence signals from feldspars: A case study

The continuous-wave IRSL (CW-IRSL) signals from feldspars are known to decay in a non-exponential manner, and their exact mathematical description is of great importance in dosimetric and dating studies. This paper investigates the possibility of fitting experimental CW-IRSL curves from a variety of feldspar samples, by using an analytical equation derived within the framework of a new model based on localized electronic recombinations of donor–acceptor pairs. 24 different types of feldspars were studied and their CW-IRSL signals are analyzed in order to establish the range and precision of numerical values for the fitting parameters in the analytical equation. The study finds systematic trends in the fitting parameters, and possible systematic differences between K and Na rich extracts from the same feldspar samples. Furthermore, results are compared with natural samples, freshly irradiated samples, and samples which had undergone anomalous fading. The results of this analysis establish broad numerical ranges for the fitting parameters in the model. Specifically the possible range of the dimensionless density ρ′ was found to be ρ′~0.002–0.01. These experimentally established ranges of ρ′ will help to guide future modeling work on luminescence processes in feldspars. Small statistical differences were found between K-rich and Na-rich fractions of the same sample. However, the experimental data shows that the parameters depend on the irradiation dose, but do not depend on the time elapsed after the end of the irradiation process. All samples exhibited the power law of decay, with the range of the power law coefficient β=0.6–1.1.

Suitability of Tanzanian Kaolin, Quartz and Feldspar as Raw Materials for the Production of Porcelain Tiles

Kaolin and quartz from Pugu; and feldspar from Morogoro were investigated to determine their suitability as raw materials for the production of porcelain tiles. From the mineralogical analysis, kaolin sample was found to contain kaolinite (Al2Si2O5(OH)4) and quartz (SiO2); quartz sample was found to contain only quartz mineral silica (SiO2); and feldspar sample was found to contain albite (NaAlSi3O8) and microcline (KAlSi3O8). The major chemical compounds found in kaolin and feldspar were SiO2 and Al2O3, and quartz sample was found to contain SiO2 and SO3. The tiles made from the raw materials and fired between 900 °C and 1200 °C were found to have the water absorption of 12.4 - 13.7%, bulk density of 1.89-1.95 g/cm3, apparent porosity of 24.1-26.0%, linear shrinkage of 0.0-1.7%, compressive strength of 107.4-380.4 kg/cm2 and loss on ignition of 3.6-6.0%. Among the studied compositions and firing temperatures, tiles made from a blend containing 40% kaolin, 45% feldspar and 15% quartz; and fired at 1100 °C were found to have the best properties for the production of porcelain tiles. This is an indication that the Tanzanian kaolin, quartz and feldspar are suitable raw materials for the production of porcelain tiles.

Light scattering by feldspar particles: Comparison of model agglomerate debris particles with laboratory samples

We present comparisons of the non-zero light-scattering Mueller-matrix elements of agglomerated debris particles with those of well-characterized experimentally measured feldspar samples at blue and red wavelengths. The only completely free parameter in our comparisons is the small-size cut-off of the sample, which was not known. The significance is that both the light scattering and the measured properties of model and real particles agree very well. While some tweaking of the particle parameters could achieve some improvement, the fits are remarkably good, with significant deviations (∼5%) occurring in portions of the polarization elements, e.g. S34. We suggest that the reason for the good fits is not that the model particles exactly represent those of the sample particles, but rather that both sets of particles belong to a class of highly irregular particles, whose high degree of irregularity dominates the resulting scattering behavior, suppressing the effect of any characteristic morphological features.

Analytical solutions for stimulated luminescence emission from tunneling recombination in random distributions of defects

Recently a new kinetic model was presented in the literature, which describes localized electronic recombination in donor–acceptor pairs of luminescent materials. Within this model, recombination is assumed to take place via the excited state of the donor, and nearest-neighbor recombinations take place within a random distribution of centers. Two versions of the model were presented which were found to be in good agreement with each other, namely an exact model that evolves both in space and in time, and an approximate semi-analytical model evolving only in time. The model simulated successfully both thermally stimulated luminescence (TL) and optically stimulated luminescence (OSL), and also demonstrated the power law behavior for simulated OSL signals. This paper shows that the system of simultaneous differential equations in the semi-analytical model can be approximated to an excellent precision by a single differential equation. Furthermore, analytical solutions are obtained for this single differential equation, and for four different experimental modes of stimulation: TL, OSL, linearly modulated OSL (LM-OSL) and isothermal TL processes. The exact form of the power law for the model is found in analytical form for both OSL and isothermal TL processes. The analytical equations are tested by successfully fitting typical infrared stimulated luminescence (IRSL) signals, as well as experimental TL glow curves from feldspar samples. The dimensionless number density of acceptors in the model is estimated from fitting the experimental IRSL and TL data. The analytical expressions derived in this paper apply also to stimulated emission via the excited state of the donor–acceptor system. However, the same analytical expression, with different numerical values for its constants, can also be applied in the case of ground state tunneling, with important implications for luminescence dating.

40Ar/39Ar dating of alkali feldspar megacrysts from selected young volcanoes of the Newer Volcanic Province, Victoria

The Newer Volcanic Province (NVP) in Victoria, with extension into south-eastern South Australia, represents the youngest chapter of Cenozoic volcanism in south-eastern Australia. However, most ages have been determined by the potassium–argon (K–Ar) method, and the age data are not comprehensive. In addition, few ages exist for the array of scoria cone volcanoes in the NVP. Seven alkali feldspar samples, mostly anorthoclase megacrysts, from volcanic centres in the NVP were used for 40Ar/39Ar dating in the present study. In geochronological order, with ages quoting 95% confidence limits, locations are Mount Franklin near Daylesford (0.110 ± 0.014 Ma), Red Rock near Alvie (0.116 ± 0.048 Ma), Lake Bullenmerri at Camperdown (0.116 ± 0.019 Ma), Ridge Road Quarry near Daylesford (2.01 ± 0.11 Ma) and Mount Kororoit near Diggers Rest (3.74 ± 0.26 Ma). Two samples from The Anakies, near Bacchus Marsh, produced discordant results suggesting a maximum age of ca. 1.9 Ma. The analyses and reported ages in the present study not only provide new geochronological data for the province, but also elucidate the difficulties in dating very young basalts using the 40Ar/39Ar dating method. These results are consistent with the erosion levels of the scoria volcanoes sampled, and indicate a major episode of explosive volcanic activity at ca. 100 ka. In contrast, the more eroded Mount Kororoit is considered to be ca. 3.7 Ma in age. The age of The Anakies is more equivocal owing to the indicated presence of excess argon and a maximum age of ca. 1.9 Ma is suggested for this locality. Given the latter results and lack of precision obtainable from the younger samples, the possibility remains that other samples contained extraneous argon and that the ages generated are thus maximum eruption ages. Analyses of additional samples from these and other localities will be required to further resolve this issue.

Geology and Economic Evaluation of Odobola, Ogodo Feldspar Mineral Deposit, Ajaokuta Local Government Area, Kogi State, Nigeria

The Odobola, Ogodo area is part of the basement complex of Nigeria and is underlain mainly by schists and intrusive granitic and pegmatitic rocks along with sediments weathered from these rocks. The granitic and pegmatitic intrusives are source of feldspar with a significant K2O component (k-feldspar). A study of the area reveals the occurrence of feldspar deposit hosted by granitic and pegmatitic intrusives. Geochemical data for the feldspar samples show average Si2O, Al2O, K2O, Na2O, CaO, Fe2O3, MgO and TiO2 contents of 65.81wt%, 16.67wt%, 10.67wt%, 5.83wt%, 0.02wt%, 0.26wt%, 0.5wt% and < 0.001wt% respectively while mineralogical results reveals average anorthite, orthoclase and albite contents of 0.42%, 85.40% and 14.06% respectively. The results of the analyses compared with those of the British international Standard (BIS) shows that the feldspar deposit can be used in industries such as glass, ceramic tiles, sanitary wares and insulators. Field and petrographic evidence show that the area is a potential source of gemstones such as tourmaline and tantalite. Mineral Resource and Reserve Estimation classify the feldspar resource as an estimated proven feldspar-bearing Reserve of about 119Million tons. Apart from feldspar, inferred Minerals Resource of quartz, tantalite and tourmaline can also be obtained from this area.

Time-resolved infrared stimulated luminescence signals in feldspars: Analysis based on exponential and stretched exponential functions

Time-resolved infrared-stimulated luminescence (TR-IRSL) signals from feldspar samples have been the subject of several recent experimental studies. These signals are of importance in the field of luminescence dating, since they exhibit smaller fading effects than the commonly employed continuous-wave infrared signals (CW-IRSL). This paper presents a semi-empirical analysis of TR-IRSL data from feldspar samples, by using a linear combination of exponential and stretched exponential (SE) functions. The best possible estimates of the five parameters in this semi-empirical approach are obtained using five popular commercially available software packages, and by employing a variety of global optimization techniques. The results from all types of software and from the different fitting algorithms were found to be in close agreement with each other, indicating that a global optimum solution has likely been reached during the fitting process. Four complete sets of TR-IRSL data on well-characterized natural feldspars were fitted by using such a linear combination of exponential and SE functions. The dependence of the extracted fitting parameters on the stimulation temperature is discussed within the context of a recently proposed model of luminescence processes in feldspar. Three of the four feldspar samples studied in this paper are K-rich, and these exhibited different behavior at higher stimulation temperatures, than the fourth sample which was a Na-rich feldspar. The new method of analysis proposed in this paper can help isolate mathematically the more thermally stable components, and hence could lead to better dating applications in these materials.

Sources of overdispersion in a K-rich feldspar sample from north-central India: Insights from De, K content and IRSL age distributions for individual grains

Abstract Luminescence dating of individual sand-sized grains of quartz is a well-established technique in Quaternary geochronology, but the most ubiquitous mineral on the surface of the Earth—feldspar—has received much less attention at the single-grain level. In this study, we estimated single-grain equivalent dose values and infrared stimulated luminescence (IRSL) ages for K-rich feldspar (KF) grains from a fluvial sample underlying Youngest Toba Tuff (YTT) deposits in north-central India, and compared these ages (corrected for anomalous fading) with those obtained from individual grains of quartz from the same sample. Both minerals have broadly similar single-grain age distributions, but both are greatly overdispersed and most grains have ages substantially younger than the expected age of the YTT deposit (∼74 ka). Almost half (45%) of KF grains used for age calculation have fading rates statistically consistent with zero, but the age distribution of these grains is as dispersed as that of the entire population. We obtained a similar distribution of ages calculated for 51 grains using their individually measured internal K contents, which exhibited only minor grain-to-grain variation. Given the lack of dependency of single-grain ages on the measured fading rates and internal K contents, and the overall adequacy of bleaching of grains collected from a sandbar in the modern river channel, we consider the spread in ages is most likely due to mixing, at the time of deposition and after the YTT event, of potentially well-bleached fluvially-transported sediments with older grains derived from slumping of riverbank deposits. Some spread may also be due to natural variations in the IRSL properties of individual KF grains.

OSL and IRSL characteristics of quartz and feldspar from southern California, USA

Southern California comprises of a wide range of diverse landscapes and environments, from high mountains with glacial and periglacial sediments to deserts with large sand dunes, extensive alluvial fans and ephemeral playas. Highly active tectonic processes has exposed ancient (c. 2 Ga) plutonic and metamorphic basement from deep within the crust, while similar Palaeozoic, Mesozoic and Cenozoic rocks are also common. A rich array of volcanic lithologies extending into the late Quaternary complement many thick sedimentary sequences that formed in equally diverse ancient environments typical of an accreting active continental margin. In some locations, notably in the Coachella Valley close to Palm Springs and the Salton Sea, low OSL sensitivity and poor characteristics restrict the application of the quartz SAR protocol to date late Pleistocene and Holocene fluvial sediments. In other locations such as the Malibu coastline, high sensitivity of the quartz OSL signal is observed, despite local source rocks being dominated by volcanic lithologies. Problems of poor quartz characteristics, along with uncertainty in predicting quartz OSL behavior for future dating campaigns poses a significant problem for projects, in particular for neotectonic contexts. While K-feldspar has been used extensively to date eolian and fluvial sediments in southern California, little information regarding signal stability is available. We explore the characteristics of both quartz and feldspar sub-samples from eolian, fluvial, lacustrine environments, in order to help develop mineral selection criteria for optical dating applications and clarify these issues. The importance of radiation quenching in quartz grains recently eroded from bedrock and the role of fires in enhancing OSL sensitivity are considered. The relative bleachability of quartz and feldspar fractions, along with thermal stability considerations is discussed. A simple test for quartz OSL signal contamination based on thermal quenching and assistance, and the susceptibility of the OSL signal to IR bleaching is introduced. ► An overview of the characteristics of OSL/IRSL signals in quartz and feldspar from Southern California, USA. ► Problems associated OSL/IRSL dating in regions with neotectonics. ► A test for OSL/IRSL signal contamination of quartz and feldspar samples.

Variable range hopping mechanism in band-tail states of feldspars: A time-resolved IRSL study

Abstract Time-resolved infra-red stimulated luminescence (TR-IRSL) technique enables an understanding of the dynamics of trapped electrons after IR excitation in the band-tail states of feldspar. This work intends to study the underlying physical mechanism of IRSL production. TR-IRSL studies were carried out on four feldspar mineral specimens of variable chemical composition and structural state. Assuming the IR excited trapped electrons make random walks in the band-tail states and recombine by tunnelling dynamically, hopping time is derived from the OFF time data of TR-IRSL. This analysis indicates that the hopping time decreases with stimulation temperature. Using Einstein diffusion equation, hopping probability is computed and is shown to obey the equation describing variable range hopping mechanism of Mott kind. Mott's parameters (hopping length and hopping energy) are then derived. Hopping length decreases with stimulation temperature whereas hopping energy increases with temperature. The average hopping length and energy are in the range of 11–18 A and 45–55 meV respectively and the diffusion constant is estimated to be in the range of 10 −10 –10 −9 cm 2 s −1 for all the feldspar samples.

Correlation Between Work Index and Mechanical Properties of some Saudi Ores

Abstract The crushing energy for applications in the mineral processing industry is usually determined by an empirical bond index, regardless of the mechanical properties of a rock. Although several attempts have been made to obtain the comminution energy based on theoretical approaches, it would be beneficial to examine this relation based on a physical concept. In this paper, some Saudi samples of bauxite, kaolinite, granodiorite, magnetite, granite, feldspar and quartz were tested for hardness, abrasion, compressive strength as well as modulus of elasticity and the bond work index of these samples was estimated. The value of the bond work index of the above samples has shown a variation from 10.8 kWh ton-1 for bauxite (high abrasion value and low compressive strength) to 20.4 kWh ton-1 for granite (low abrasion value and high modulus of elasticity). The correlation between the abrasion value (X2) and work index (Wi) is found to be Wi = −1.8 Ln(X2) + 11.5 with a correlation coefficient of 0.80.

CORRELATION BETWEEN BOND WORK INDEX AND MECHANICAL PROPERTIES OF SOME SAUDI ORES

The crushing energy in mineral processing industry is usually determined by empirical Bond index, regardless of the mechanical properties of a rock. Although several attempts have been made to obtain the comminution energy based on theoretical approaches, it would be beneficial to examine this relation based on physical concept. In this paper, some Saudi samples of bauxite, kaolinite, granodiorite, magnetite, granite, feldspar and quartz were tested for hardness, abrasion, compressive strength and modulus of elasticity and the bond work index of these samples were estimated. The value of Bond work index of the above samples has shown a variation from 10.8 kwh ton-1 for bauxite (high abrasion value and low compressive strength) to 20.4 kwh ton-1 for granite (low abrasion value and high modulus of elasticity). The correlation between the abrasion value(X2) and work index (Wi) is found to be Wi = -1.8 Ln (X2) + 11.5 with correlation coefficient of 0.80.

Maxwell–Wagner relaxation in common minerals and a desert soil at low water contents

Penetration of 100- to 1000-MHz ground-penetrating radar (GPR) signals is virtually non-existent in arid and desert soils despite their low water content and moderate conductivity, the latter of which cannot explain the loss. Under the hypothesis that strong dielectric relaxation supplements DC conductivity to cause high intrinsic attenuation rates, we compared the complex permittivity of a desert soil sample with that of controlled samples of quartz, feldspars, calcite, coarse and crystallite gypsum, kaolinite and montmorillonite. The soil had 80% quartz, 10% feldspars and 10% gypsum by weight, with the latter composed of crystallites and crustations. All samples had 4–7% volumetric water content. We measured permittivity most accurately from 1.6 MHz to 4 GHz with Fourier Transform time domain reflectometry, and used grain sizes less than 53 μm. All samples show low-frequency dispersion with the soil, gypsum crystallites and montmorillonite having the strongest below 100 MHz, the highest attenuation rates, and conductivity values unable to account for these rates. The soil rate exceeded 100 dB m− 1 by 1 GHz. Through modeling we find that a broadened relaxation centered from 2 to 16 MHz sufficiently supplements losses caused by conductivity and free water relaxation to account for loss rates in all our samples, and accounts for low-frequency dispersion below 1 GHz. We interpret the relaxation to be of the Maxwell–Wagner (MW) type because of the 2- to 16-MHz values, relaxation broadening, the lack of salt, clay and magnetic minerals, and insufficient surface area to support adsorbed water. The likely MW dipolar soil inclusions within the predominantly quartz matrix were gypsum particles coated with water containing ions dissolved from the gypsum, and the conducting water layers themselves. The inclusions for the monomineralic soils were likely ionized partially or completely water-filled interstices, and partially filled galleries for the montmorillonite. The low water content may be necessary to help isolate these inclusions. For our common, low conductivity minerals, the MW contributions to attenuation rates are significant above 10 MHz, whereas they are significant above about 100 MHz for the more conductive minerals and soil.

Natural radioactivity of materials used in industry and construction in Serbia

Four different kinds of materials (feldspar, gypsum, clay and kaolin) commonly used in building construction and industry in Serbia were analyzed for their natural radioactivity, using gamma spectrometry. The radium equivalent activity, , the absorbed dose rate, , the annual effective dose, , and the external hazard index, , were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The radium equivalent activities calculated in all samples are lower than the maximum admissible value 370 Bq kg−1 set in the UNSCEAR report.[ 1 ] The absorbed dose rate in air was found to vary from 0.02 to 0.19 μGy h−1. Considering the fact that the average gamma dose rate indoors in Europe is 0.07 μGy h−1 [ 2 ], gamma dose rate calculated for feldspar, clay and kaolin samples exceed this limit. The obtained results for annual effective dose exceed limits of 0.41 mSv[ 1 ] for feldspar, clay and kaolin samples. If the exceeds unity, we might conclude that the potential external dose(s) to exposed individual(s) will exceed the acceptable level, and some action may be required. The obtained values of are lower than unity for all investigated samples. All samples were measured immediately after preparation, except 10 samples of feldspar, because a comparative analysis were made between 215 samples which were measured immediately after preparation and 10 samples which were measured after radioactive equilibrium was reached in order to detect differences in the obtained concentrations.

A survey of culturable aerobic and anaerobic marine bacteria in de novo biofilm formation on natural substrates in St. Andrews Bay, Scotland

This study reports a novel study of marine biofilm formation comprising aerobic and anaerobic bacteria. Samples of quartz and feldspar, minerals commonly found on the earth, were suspended 5m deep in the North Sea off the east coast of St. Andrews, Scotland for 5weeks. The assemblage of organisms attached to these stones was cultivated under aerobic and anaerobic conditions in the laboratory. Bacteria isolated on Marine Agar 2216 were all Gram-negative and identified to genus level by sequencing the gene encoding 16S rRNA. Colwellia, Maribacter, Pseudoaltermonas and Shewanella were observed in aerobically-grown cultures while Vibrio was found to be present in both aerobic and anaerobic cultures. The obligate anaerobic bacterium Psychrilyobacter atlanticus, a recently defined genus, was identified as a close relative of isolates grown anaerobically. The results provide valuable information as to the main players that attach and form de novo biofilms on common minerals in sea water.

Natural radioactivity and Rare Earth elements in feldspar samples, Central Eastern desert, Egypt

The pegmatite bodies of the Eastern Desert of Egypt are widely distributed especially along the Marsa-Alam-Idfu road. The Abu Dob area covers about 150km(2) of the Arabian Nubian shield at the central part of the Eastern Desert of Egypt. Most of the pegmatite is zoned; the zonation starts with milky quartz at the core followed by alkali feldspar at the margins. The feldspars vary in color from rose to milky and in composition from K-feldspar to Na-feldspar, sometimes interactions of both types are encountered. Thirteen feldspar samples were collected from different locations in the Abu Dob area for measuring the natural radioactivity of (238)U, (232)Th and (40)K using an HPGe detector. The variation in concentration of radionuclides for the area under investigation can be classified into regions of high, medium and low natural radioactivity. The average concentration in BqKg(-1) has been observed to be from 9.5 to 183675.7BqKg(-1) for (238)U, between 6.1 and 94,314.2BqKg(-1) for (232)Th and from 0 to 7894.6BqKg(-1) for (40)K. Radium equivalent activities (Ra(eq)), dose rate (D(R)) and external hazard (H(ex)) have also been determined. In the present work, the concentration of rare earth elements are measured for two feldspar samples using two techniques, Environmental Scanning Electron microscope XIL 30 ESEM, Philips, and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The existence of rare earth elements in this area are very high and can be used in different important industries.